Questions about front/rear speakers amp tuning

Noobie here so bare with me , I just finished my first car audio install on my 01 taco. Everything went surprisingly smooth considering I have literally never installed any speaker wire, amp, headunit EVER. I basically started by changing out my stock stereo with an alpine headunit and wired it to a harness and installed it with no problems. I then changed out all my speakers with alpines and re-wired them with 16 gauge running them to my amp. Then connected pwr and ground and blue signal wire and everything went as planned. 6x8's alpine type rs in front and type s in rear. 4 channel amp 75 rms to each speaker. Although I love deep bass, i left the subwoofer out bc I like to have room in my ext cab taco and honestly only care about having a crisp/loud sounding system.

I honestly expected something to go wrong, mainly during the headunit install but I just took my time and with my knowledge from lurking here and using common sense everything went well.

I am now at the stage of fine tuning my speakers with proper gains and I am a little unsure how exactly to achieve this. I know the typical- turn gains to min, crank speakers up until u hear distortation, back speakers down then turn gain up until they distort then back off blahblahblah. My headunit goes to 35 volume and my speakers sound loud with no distort at 35. I have kept all the levels on my headunit at 0 or neutral bc I understand it's better for the speakers. From the start I turned the front and rear gains on my amp just a nudge maybe a quarter of the way. Then I turned the rear gains up a little more b/c I realized that my front speakers are louder than my rear and want them to be the same loudness. I know im kinda rambling here.. but is it normal for the rear speakers to be a little quieter than the front? Is it ok to turn the bass from headunit to atleast 1 or 2? I have yet to hear any distortion so im kinda of itching to crank up the gains some more but dont want to create any sort of clipping and what not. Any other tuning suggestions or things i can change on my amp dbs or watever